The other day, pulling up to a stoplight in my '03 MCS, I noticed shaking, a wheezy/rattling engine note, and the dreaded flashing CEL (which went solid after a minute, presumably once the computer turned off fuel to the bad cylinder). After limping the rest of the way home, my code reader confirmed a misfire on #2.

I was hoping it was ignition-related—I still had the original coil pack and spark plug wires ~155,000 miles in—but replacing those parts and the plugs didn't buy me anything. I cleared codes and let the engine run for 30 seconds or so to make sure it didn't get better. Pulling the spark plugs again, I noticed that the new #2 plug was more significantly more oily than its neighbor. Too, there was a little wisp of smoke coming out of the #2 plug well.



What am I looking at? Bad/clogged injector (although it's been smelling like it's running rich)? Or something more serious like piston damage? (The engine did run a quart low on oil once or twice in the past, before I fixed the crank seal.)

 

With all the oil on the threads of the plug it makes me think you have a valve cover gasket leak. Oil leaking into the spark plug well can cause misfires. Did you notice this? If so, clean the plug and the rubber boot on the wire, button it back together and fire it up.

 

do a compression check on all cylinders then a leakdown test on #2 assuming it is not sealing correctly. Oil on the plug threads can be a leaky valve cover gasket, but on the tip... that does not look good.

I had uneven compression numbers that I suspected was carbon on the valve seats, did a partial sea foam treatment thru a vacuum line and noticed it ran noticeably better afterwards (found I had an exhaust leak in the process). Not night & day but definitely stronger pull from it. Still need to fix the exhaust leak and finish... once done I will bet the compression numbers will be more in line with what I'd expect. First test pointed me to a rebuild with on cylinder all the way down to 90 psi, which I dont buy the motor needs a rebuild, just does not behave like it, pulls very strong and does not behave like a worn motor.

I would also suggest running a stiction eliminator (Hot Shots Secret) in the crank to free up any stuck rings and remove any deposits. I also believe it would ensure the chain tensioner does not stick. Currently have it in mine now and it will be in there for the remainder of the OCI. Some background on the stuff.. My Ram motor had been using up to 4 qts of oil in 7000 miles (380k on the clock at the time), figured I was looking at a rebuild in the future, ran the SE as an experiment and the oil loss dropped to a consistent 1~1.5 qts over the 10k OCI. Now at 450k miles its starting to creep back up to approx 2qts over that 10k OCI.

 

Do you have first hand experience on this? I have a leak on #2 as well but dont have any mis-fire problem

 

I don't think it's a leaky valve cover gasket—the spark plug itself is clean.

Have a recommended compression tester? I figure I'll need one with some kind of rigid connector so I can get it down into the spark plug well. I don't have a compressor, so I'd have to have the leakdown test done somewhere.

I have a little borescope I can borrow from a friend tomorrow, to do some visual inspection of the cylinder. What should I see when I look?

 

Something like this... The hose will reach down there w/o issues.


better one... https://www.otctools.com/products/co...ion-tester-kit

 

Thanks!

 

Steve05ram360: I have the same kit and it didn't seem to seal properly. Because the plug well is so deep on a Mini this type of compression device can only be hand-tightened using the rubber hose. Have you used it on your Mini (not your Ram) and did you get valid compression readings across all cylinders?

 

Well, it looks like it's pretty dead. I didn't want to run the engine to warm it up properly for a compression test, but the cold numbers are:

125 psi
30 psi
130 psi
130 psi

Which pretty much screams blown rings, I suspect? If it were a valve stuck open, I'd expect no compression at all on that cylinder, and I don't/didn't get the puff of blue smoke in the morning I'd expect from bad valve seals. e: for some extra confirmation, I put a capful of into the cylinder through the spark plug well, and got 40psi.

If so, I guess it's time to put up an ad over in the classifieds section. Much as I love this car, I don't think I have the time to invest it making it roadworthy again—hopefully, I can find someone who'll either do that, or use it to keep another one going.

 

I would suspect a burnt valve with those numbers....

Bryan

 

Even with the change in compression with a bit of oil in the cylinder? I guess that might just be reducing blowby since the engine's cold, come to think of it.

e: with the oil-in-cylinder trick on 1, I went from 125psi to 180psi, so maybe so.

 

with 30lbs compression, and you add oil, if it was rings, test pressure should have went higher.....you have a large leak somewhere....burnt valve, head gasket, maybe burnt piston could be possible also

Time for a leakdown test with #2 piston at exact TDC.....either that, or just pull the cylinder head and have a good look around....it's gonna have to come off anyway

Bryan

 

I think it's probably still time for me to move on from the car, regardless—pulling the head is a bit beyond what I'm comfortable DIYing, and I don't think my mechanic's going to come back to me with an estimate that I'm ready to pay.

Thanks for your help/insights, though.

 

The one I have is old... really old... I've had it decades. It has a rubber o-ring at the bottom where the threads go down into the head, When I did my mini, I got repeatable numbers out of it when I repeated the test, all the cylinder pressures were with 5psi of the original numbers. The o-ring is going to be the seal on that cylinder (Obviously) and the key is to give it a good twist at the top before attaching the gauge. Repeatability is key, if you can get the same numbers out of it on the same cylinders then you can build confidence that the numbers are correct. (FWIW, I'm a test engineer by trade so data collection is what I do for a living)

 

Since you suspect broken rings, you loose nothing by doing a sea foam treatment on the intake and running the stiction eliminator in the oil. My experience with the oil loss on the truck and the way it ran, I figured I was heading towards a rebuild. Now what... year and a half later??? motor still is running with no end in sight.

What I'd do is dump in the 2 quarts they recommend, (take 2 quarts out as to not over fill it), then fire it up and let it idle for a good bit then re-do the compression test. If you see improvement, fire it back up and run it some more. You loose nothing since you already think your in for a rebuild.

If it were my engine, that is what I'd do, worst case your buying a car-part.com engine and doing a swap.

 

I would give the suggestion a shot... you never know and the $50~75 bux spent getting the suggestions done is a lot cheaper than any work & a new car.

When I get the rest of the sea foam treatment done on my engine, will report back compression numbers.

 

Worth a shot, I guess, although I'm not super-hopeful.